1. Field of the Invention
The present invention relates to a MIS type semiconductor photoelectric conversion device.
2. Description of Prior Art
There has heretofore been proposed a PN or PIN junction semiconductor photoelectric conversion device.
The PN or PIN junction semiconductor photoelectric conversion device has such a construction that P and N type regions are formed in a semiconductor wafer or layer so as to provide therein a PN or PIN junction as a barrier. In this case, the P type region is formed by highly doping into the semiconductor wafer or layer a P type impurity which is potentially harmful to human health, and the N type region is also formed by high doping of an N type impurity which is similarly potentially harmful.
Accordingly, the PN or PIN type semiconductor photoelectric conversion device has the defect that its manufacture entails potential dangers to human safety and health.
Further, a Schottky junction semiconductor photoelectric conversion device has hitherto been proposed. The Schottky junction semiconductor photoelectric conversion device has such a construction that a metal of larger work function than a semiconductor wafer or layer is contacted therewith to form a Schottky junction as a barrier. The barrier by the Schottky junction has a high degree of temperature dependence; for example, when it is heated at 150.degree. C. for a short time, the height of the barrier undergoes a change. Accordingly, the Shottky semiconductor photoelectric conversion device is not of practical use on the ground that the temperature dependence is large.
Moreover, a MIS type semiconductor photoelectric conversion device has been proposed. The conventional MIS type semiconductor photoelectric conversion device usually has a semiconductor wafer or layer, an insulating layer which is formed thereon to a thickness small enough to permit the passage therethrough of a tunnel current and is light transparent, a first electrode which is formed on the insulating layer and is light transparent and a second electrode which is formed on the semiconductor wafer or layer on the opposite side from the insulating layer. Since the MIS type semiconductor photoelectric conversion device of such a construction has a barrier formed by the insulating layer, when light is incident to the semiconductor wafer or layer from the side of the first electrode, a photoelectric conversion function is provided.
In such a MIS type semiconductor photoelectric conversion device, the barrier is formed by the insulating layer, not by the PN or PIN junction which is formed in the semiconductor wafer or layer, so that the manufacture of this device is free from such dangers as encountered in the manufacture of the PN or PIN junction semiconductor photoelectric conversion device. Further, since the barrier is formed by the insulating layer, not by the Schottky junction, the barrier has substantially no temperature dependence. Accordingly, the MIS type semiconductor photoelectric conversion device is more useful than the PN or PIN junction and the Schottky junction semiconductor photoelectric conversion devices.
In the abovesaid conventional MIS type semiconductor photoelectric conversion device, however, since the semiconductor wafer or layer is used as a supporting member for the insulating layer and the first and second electrodes, too, it must be formed thick; namely, an expensive material is required therefor in quantity. Further, such a construction introduces difficulties in the manufacture of this device. In addition, the first electrode lies on one of two opposing surfaces of the semiconductor wafer or layer serving as the supporting member and the second electrode lies on the other surface; hence, this causes inconvenience to the use of the device.